U.S. Pat. Nos. 4,116,856; 4,116,858; and 4,159,311 disclose preparation of, and uses of, ion exchange resins having incorporated therein crystalline LiX.2Al(OH).sub.3, where X is halide, especially chloride. Our co-pending Ser. No. 095,691 filed Nov. 19, 1979 discloses a method for maximizing the amount of these crystalline lithium halide aluminates in the exchange resins. These patents and our co-pending Ser. No. 095,961 are incorporated herein by reference.
The present invention pertains to the obtaining of high purity lithium halide solutions from the use of such resin/aluminate composites. When these composites have been employed to absorb Li.sup.+ ions from brines by having the Li.sup.+ taken up into the aluminate crystals, there still remains in the interstices of the composite some of the brine from which the Li.sup.+ ions have been absorbed. When the brine contains other metal ions (i.e., other than alkali metal ions) such as alkaline earth metal ions, then when an aqueous wash is employed to elute desired Li.sup.+ ions from the crystals, the effluent also contains these other metal ions which were in the interstices but which were not in the crystal structure.
It has now been found that the use of a concentrated pure Na halide brine washing step before the water-washing step used for Li.sup.+ leaching, results in washing out the metal ions (such as alkaline earth metal ions) without leaching out a significant amount of the Li.sup.+ in the aluminate crystals. Then when water is employed to leach out the Li.sup.+ in the aluminate crystals, the only other metal ions present in any appreciable amount in the effluent are those of the Na halide brine.